Baths for the production of metal electroplates



United States Patent 3,075,899 BATHS FOR THE PRODUCTION OF METAL ELECTROPLATES Wennemar Strauss and Wolf-Dieter Willmund, Dusseldorf-Holthausen, Germany, assignors to Dehydag, Deutsche Hydrierwerke G.m.b.H., Dusseldorf, Germany, a corporation of Germany No Drawing. Filed Apr. 20, 1959, Ser. No. 807,290 Claims priority, application Germany Apr. 26, 1958 12 Claims. (Cl. 204-52) This invention relates to a method and bath for obtaining bright metal electrodeposits. It more particularly relates to the use of sulfonic acid derivatives of thioamides or isothioamides for obtaining bright metal electrodeposits.

From German Patent No. 837,029, it is known that acid copper baths can be improved by the addition of thioacetamide as a brightening agent. It was found, however, that the brightening eifect achieved thereby is only moderate. The subsequent polishing of the electroplated objects requires a separate step and it is connected with a considerable abrasion of the per deposits.

It is an object of this invention to provide a method and bath for obtaining bright metal electrodeposits which require no mechanical polishing.

Another object of this invention is to provide electroplating bath brightener compounds which have high stability and long life.

It is a further object to provide a method for producing electroplating brightener compounds. 7

These and other objects of our invention will become apparent as the description thereof proceeds.

We have now found that the brightening efiect on electrodeposited metal, and particularly copperplates, can

'be substantially improved, wherebya subsequentpolishing step becomes, as a rule, completely superfluous, by

previous applied copv adding to the acid electroplating bath acyclic or cyclic thioamides or isothioamides, which contain a sulfonic acid group which is attached to the nitrogen atoms of the thioamide or isothioamide through'a' hydrocarbon radical. These compounds are sutficiently soluble in the electroplating baths, very stable .and are only very slowly consumed in these baths.

The compounds. used as brighteningragents in accordance with the invention have the general. structural for .wherein R, R and R", represent hydrocarbon radicals,

and R and/or R may also be hydrogen atoms. R and R may further form a polymethylene chain, so that the -thioamide group is a member ofa heterocyclic ring.

'IThehydrocarbon radicals are R and R", may carry 3,075,899 Patented Jan. 29, 1963 2 substituents such as halogen, cyano, thiocyano and/or hydroxyl groups, or they may also be interrupted by heteroatoms or heteroatom groups, and they may par-- ticularly contain additional thioamide and isothioamide groups. Brightening agents of this type are, for example,

the water soluble salts of the following compounds:

'Thioacetamide-N-( Z-hydroxypropane-w-sulfonic acid),

Thioacetamide-N-(2-chlorpropane-w-sulfonic acid), Ethylene-1,2-bis- ['thioacetamide-N,N-bis-(propane-woulfonic acid) -N,N'],.

Ethylene-1,2+bis-[thioac'etarnide-N,N'-bis-(butane-w-sul-v fonic acid)-N,N'], Butyrothiolactam-N-(propane-w-sulfonic acid), Valerothiolactam-N-(propane-w sulfonic acid),

,Caprothiolactam-N-(propane w-sulfonic acid),

Caprothiolactam-N-(butane-w-sulfonic acid) N-(propane-w-s' ulfonic acid)-thioacetimino-S-ethylester,

1 Thiopicolinic acid -.N.- methyl N (propane o sul- N-(butane-w-sulfonic acid)-thiobenzimino-S-n-butylester,

fonic acid)-arnide N'-(propane-w-sulfonic acid)butane,

: Thiopicolinic acid-N-phenyl-N-(propane-w-sulfonic acid),-

am-ide-N'-(propane w-sulfonic acid) betain.

The production of these compounds takes place, for example by reaction of the thioamides or isothioamide-S- esters with' organic amino sulfo-nic acids'or their salts. The isothioami'de S s'ters may also be reacted with haloalkanesulfonic acids or sultones. Suitable sulfonic .acids are. primarily those of the. aliphatic or aromatic series which react with the "thioamides or isothioamides in aqueous or non-aqueous, for example in' alcoholic solution or suspension. The reaction with the sultones may also take place in the -molten state. The reactions proceed readily and smoothly and as a rule produce high yields,

. so. that the, end product may be used as such, possibly after neutralization, and advantageously in'the form of 1 corresponding aqueous solutions.v

In order to broaden the efiective range of the worle ing temperature in acid baths, thioamides or isothioamides which generally contain no sulfonic acid groups may be simultaneously used. In this manner'the working temperature may be increased up to .55" C. and

3 higher without unfavorably' influencing the brightness and ductility of the electrodeposits. In addition, other known brightening agents may also be added to these electroplating baths.

In some cases it is recommended to use simultaneously wetting agents and ductility improving agents, such as amino compounds free from carboxyl groups. The addition of the last-mentioned agents has the effect that inorganic impurities, such as those which are present in the hardness components of water and in technical grade metal salts, will not have a detrimental eifect upon the brightening effect.

Amino compounds free from carboxyl groups of this type are, for example, N,N,N',N-tetraethyl-l,3-diamino propanol-2; N,N,N',N'-tetrahydroxyethyl-ethylene diamine-Z diethylamino-ethylchloride l; N,N dimethyl 4- bromoanilin-3-diethylamino-l-chloropropanol-Z; as well as halogen salts of quartenary ammonium compounds which have been formed from the last-mentioned substituents by internal rearrangement, as well as sulfuric acid derivatives which are derived from the first-mentioned amino compounds, such as N,N,N',N'-tetra-n-butyl-l,3- diaminopropanol-Z-monosulfuric acid ester and piperazine-N,N'-bis-(2-hydroxypropane-sulfonic acid).

The brightening agents according to the invention may also be advantageously used in an acid direct copper plating process, that is a process in which the, metal ob jects are treated prior to electroplating in an acid pickling bath containing inhibitors with a high inhibiting effect, and subsequently directly electroplated in said copper baths containing the agents acording to the invention, without intermediate rinsing.

The brightening agents according to the invention may he used in acid, cyanide and alkaline electroplating baths for the production of copper, zinc, cadmium, tin, brass, bronze, silver and gold electroplates. The brightening agents are added to the baths in quantities from 0.001 gm./liter to 5 gm./liter, preferably from 0.05 to 0.03 gin/liter, and the electroplating process is carried out at bath temperatures from room temperature to 60? C., in alkaline baths up to 90 C., and'in current density ranges from 0.5 a'mp/dm. to 16 amp/dink, in'alkaline baths up to 40 am'pJdmP.

The following examples are set forth to enable persons skilled in'the art to better understand and practice our invention and are not intended to be limitative.

Example I A customary acid copper electroplating 'bath which contained 210 gin/liter CuSO .5H O, 60 gm./ liter H 80, and as' brightening agent 2 gmJliter of a condensation product of dodecylalcohol and mols ethylene oxid Which had been 25% transformed into. the sulfuric acid ester, was modified with 0.3 gun/liter of the sodium saltof"caprothiolactam-N-(propane-w-sulfonic acid) having the structural formula Ii QHs-CHa-C mom nt usom A; brightening agent for the acid copper hath illustrated in Example I:

Brightening Agent Thioacetamide-N- (propaue-w-sulfouic acid) Thioacetarnide-N- (methane sullonic acid) Thioiormemide-N-(butane-arsulfouic acid) Thioacetamide-N-butyl-N-(propaue-w-sulfonic acid). Thloaeetamide-N-cyclohexyl-N- (propane-w-sulfonic acid) ThioacetamideN-benzyl-N-(propane-w-sulionic acid) Thiobeuzamide-N-(propanc-m-sulfonic acid) Thiopicoliuic acid N methyl N (propane m sulionic acid)-amide-N- (propane-wsultouic acid)-betalne Thl ipicolinic acid N phenyl N (propane w sulianic acid)-amide-N-(propane-osnlfonic acid)-betalue Ethylene 1.2 bis [thioacet-amide N,N bis (propanem-sulionic aeid)-N,N'] N (propane w sulfonic acid) thioacetimino S ethylester N-(propane-w-sulfouie acid)-thioacetimluo-S-pr0pylester.. N- (butauew-sulionic acid)-tliiobenzimino-S-n-butylester.... N-(propane-wsuliouic acid)-thioacetimino-S-benzylester. N (propane w sulionic acid) thioacetimino S o (pchlorophenyl) ester N-(2-hydroxypropane-wsulloulc acid)-thiobutyrlmiuo-S- cyclohexylester N (propane w sultonic acid) 2 hydroxythiobenzimlno S-ethylester Example Hi Sheet iron or sheet steel was electroplated in an acid zinc electroplating bath which contained 200 gm./liter zinc sulfate, 0.5 to 2 gm./liter glacial acetic acid and, as brightening agent, 1.5 gm./liter thioacetamide-N-methane sulfonic acid within the current density range, of l to 6 ampJ-dm. and at room temperature. Bright zinc electroplates were obtained. Without the above brightening agent additive the zinc electroplates are dull under otherwisev identical conditions.

Example IV Example V Uniform brass electroplates. on iron and steel objects were. obtained when these materials were electroplated in a bath which contained 30 gm./liter copper cyanide, 9.4 gm./liter zinc cyanide, 56 gm./liter sodium cyanide,

l 30 gm./liter N-hydro soda and, as brightening agent, 0.5

gm./liter of the sodium salt of thiopropionamide-N- (haphthalene-S-sulfonic acid). The electroplating process was advantageously carried out at 50 to 60 C. at current densities of 1 to 4.5 amp/din By further adding 1.2 gm./liter of the sodium salt of ethylene-1,2- bis[thioacetamide N,N"-bis (butane a) sulfonic acid)] the uniform brass electroplates became full-bright.

Example VII A tin electroplating bath which contained 420 gm./ liter potassium stannate and 22.5 gm./liter potassium hydroxide was modified with 3.5 gm./liter of potassium salt of caprothiolactam Ns(propane-w-sultonic acid). At current densitiesfofZ to 40 amp/din. and attemperatures Example VIII Thioacetamide N (propane w sulfonic acid) sodium salt having the following structural formula:

CHa-(f-NH-CHI CHICHZ-S O N8 may be prepared by the following method. 16.1 gm./ liter (0.1 mol) w-aminopropanesodium sulfonate and 7.5 gm. (0.1 mol) thioacetamide were dissolved in 50 cc. water and the solution was heated for some time to 80 C., whereby ammonia escaped. After the evolution of ammonia had ceased the solution was evaporated in a vacuum. 20.7 gm. of a greenish-yellow product remained as a residue, which was purified by dissolving it in a small amount of water and reprecipitating it by adding an ether-acetone mixture. The use of this compound as a brightening agent is illustrated in Example II.

Example [X The sodium salt of N-(propane-w-sulfonic acid)-thioacetimino-Sbenzylester having the following structural formula:

CHr-(fi-SCHr- N-CHzCHgCHz-SOsNB may be prepared by the following method. 20.1 gm. of

the hydrochloride of thioacetamino-S-benzylesters were Subsequently, in order to remove components having a bad odor, the solution was extracted with ether. The aqueous solution of the sodium salt of N-(propane-wsulfonic acid)-thioacetimino-S-benzylester is employed as illustrated in Example II.

While we have set forth specific embodiments and preferred modes of practice of our invention, it will be understood that we do not intend to be limited thereby, and that various changes and modifications may be made within the spirit of the invention and the scope of the appended claims.

' We claim:

1. A method for producing bright metal electrodeposits on a base metal, which comprises adding as a brightening compound to the electroplating bath solution containing a compound of the metal to be electrodeposited, a sulfonic acid compound having a structural formula, selected from the group consisting of:

and

and their alkali metal salts, wherein R and R are selected from the group consisting of hydrogen, hydrocarbon radicals, and taken together a polymethylene chain of a heterocyclic ring, and R" is a hydrocarbon radical, said brightening agent being added in sufiicient amount to obtain said bright electrodeposits.

and

and their alkali metal salts, wherein R and R are selected from the group consisting of hydrogen, hydrocarbon radicals, and taken together a polymethylene chain of heterocyclic ring, and R" is a hydrocarbon radical, and

in addition compounds having a structural formula selected from the group consisting of s and N RII R-C wherein R, R and R" represent groups as above defined, said brightening agent being added in sufiicient amount to obtain said bright electrodeposits.

' 5. A method for producing bright copper electrodeposits on a base metal, which comprises adding as a brightening compound to an acid copper electroplating bath solution a sulfonic acid "compound having a structural formula, selected from the'group consisting of:

and

and their alkali metal salts, wherein R and R' are selected from the group consisting of hydrogen, hydrocarbon radicals, and taken together a polymethylene chain of a heterocyclic ring, and R is a hydrocarbon radical, said brightening agent being added in sufficient amount to obtain said bright electrodeposits.

6. The method of claim 1 wherein the amount of brightening compound added is from about 0.001 to about 5 g./ 1.

7. An electroplating bath for producing bright metal electrodeposits on base metals which comprises an aqueous solution of a compound of the metal to be deposited and a brightening compound which is a sulfonic ama s acid compound having a structural formula, selected from the group consisting of: i i r R R"SO;H

and

and their alkali metal salts, wherein R and R are selected from the group consisting of hydrogen, hydrocarbon radicals, and taken together a polymethylene chain of a heterocyclic ring, and R" is a hydrocarbon radical, said brightening agent being added in sufficient amount to obtain said bright electrodeposits.

8. An electroplating bath as defined in claim 7 selected from the group consisting of acid, cyanide and alkaline baths.

9. The bath of claim 7 wherein said electroplating bath contains in addition amino compounds free from carboxyl groups.

10. An electroplating bath for producing bright metal elec'trodepositson base metals which comprises an aqueous solution of a compound of the metal to be deposited, a brightening compound which is a 'sulfonic acid compound having a structural formula, selected from the group consisting of:

and

8-H and their alkali metal salts, wherein R and R are selected from the group consisting of hydrogen, hydrocarbon radicals, and taken together a'polyrnethylene chain of a heterocyclic ring, and R is a hydrocarbon radical, and in addition compounds having a structural formula selected from the group consisting of ,S RI wherein R, R and R" represent groups as above defined, said brightening agent being added in sufficient amount to obtain said bright electrodeposits.

11. An acid copper electroplating bath for directly producing bright copper electrodeposits on base metals which comprises an aqueous acid solution of a copper salt and a brightening compound which is a sulfonic acid compound having a structural formula, selected from the group consisting of:

and

N.-- R"-s0,rr R-G SR and their alkali metal salts, wherein R and R are s e lected from the group consisting of hydrogen, hydrocarbon radicals, and taken together a polymethylene chain of a heterocyclic ring, and R is a hydrocarbon radical, said brightening agent being added in sufficient amount to obtain said bright electrodeposits.

12. The bath of claim 7 wherein the amount of brightening compound added is from about 0.001 to, about 5 grn./1iter.

References Cited in the file of this patent UNITED STATES PATENTS 2,489,538 Phillips et al. Nov. 29, 1949 2,663,684 Pierce Dec. 22, 1953 2,742,413 Cransberg et al. Apr. 17, 1956 2,772,309 Doerner Nov. 27, 1956 2,806,879 Kaiser et al Sept. 17, 195.7 2,830,014 Gundel et al. Apr. 8, 1958 2,837,472 Gundel et al. June 3, 1958 2,849,351 Gundel et a1. Aug, 26, 1958 2 ,849,352 Kirstahler et a1 Aug, 26, 1958 2,903,403 Strauss Sept. 8, 1959 2,905,602 Kirstahler et al. Sept. 22, 1959 2,937,978 Strauss et al, May- 24, 1960 2,950,235 Strauss et al. Aug. 23, 1960 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No, 3,075,899 January 29, I963 'Wennemar Strauss et 310 It is hereby certified that error appears in the above numbered patv ent requiring correction and that the said Letters Patent should read as corrected below.

Column 3, line 38, for "0003" read u 003 Signed and sealed this 3rd day of September 1963,

(SEAL) Attest: ERNEST w. SWIDER DAVID LADD Attesting Officer Commissioner of Patents 

1. A METHOD FOR PRODUCING BRIGHT METAL ELECTRODEPOSITS ON A BASE METAL, WHICH COMPRISES ADDING AS A BRIGHTENING COMPOUND TO THE ELECTROPLATING BATH SOLUTION CONTAINING A COMPOUND OF THE METAL TO BE ELECTRODEPOSITED, A SULFONIC ACID COMPOUND HAVING A STRUCTURAL FORMULA, SELECTED FROM THE GROUP CONSISTING OF: 